| 摘要 |
583,582. Cables. BRITISH INSULATED CABLES, Ltd., and CARSTEN, H. R. F. Nov. 6, 1944, No. 21719. [Class 36] A conductor for high frequency currents is built up of a tubular braid of helically interlaced elements, each consisting of one or more secondary groups of wires L, R, each group being formed by two or more helically twisted primary groups of wires S, comprising seven or more insulated wires. In Fig. 2, each primary group S comprises 19 enamelled copper wires of 40 s.w.g. strand with a .75 inch lay, the secondary groups L, R being formed by helically twisting four primary groups S with a left or right handed 3 inch lay, respectively, each group S comprising seven or more wires, lightly insulated from one another, as by enamelling. The twelve elements B are each formed by twisting together a group L and a group R, and are braided together at an angle of 40 degrees to the axis over a flexible tube A of metal, rubber or synthetic rubber-like material, which may serve for circulation of a cooling medium. Since most braiding machines give the elements an additional twisting during the braiding operation, one half in a right-handed and one half in a left-handed direction, two sets of elements may be employed so that the direction of lay in the braid is in the same direction as that in the previous twisting operation. An insulated tube C of polyethylene, polyvinyl chloride or other low loss material is extruded, or applied by lapping over the braided elements B, and over this may be applied a further braid D, Fig. 1, enclosed in a lead or other metal sheath or an insulating and/or protective covering E. According to the Provisional Specification there may be an intervening layer of protective material between the metal sheath and the braid D. The thickness of the wires is between 30 and 48 s.w.g., being determined by the condition that the diameter in millimetres is approximately equal to the reciprocal of ten times the square root of the frequency in megacycles per second. |
